High voltage transmission line connection



y 4, 1934. A. o. AUSTIN ET AL HIGH VOLTAGE TRANSMISSION LINE CONNECTION Filed Feb. 18. 1929 Fig] My mmm N N m R E mb m Vf T. Nw

In A 7 MM Patented July 24, 1934 Em aoFFIcE *HIGHVOLTAGE TRANSMISSION #ooNNEo r-ioiv Arthur O.Austin,- near Bar-Berton, and 5 William A. Hillebrand; Akron, Ohio; assignors, by-mesne assignments, to The fOhio"Bia'ss company, Mansfield, Ohio; a. corporation "ofl l'ew' Jersey Application February: is; 1929; SeriaFNo; 340,679

3 Claims.

" This invention relatesto means forconnecting relays or other apparatus with high voltage transmission-lines and 'hasfor one of its objects the provision ofa connection'which sha1l -be more reliable and more economicarthan-con- 'nections heretofore provided.

Another object is to" provide a transmission "line connection which shall 'be of improved construction and operation.

" Other objects and advantageswill appear from "the following description.

"The invention is exemplified in thecombina- *tionand'arrangementof parts shown in the accompanying drawing and described in the following specification, and it is more particularly pointed out in the appended claims.

"In the'drawing: Fig. 1 is a diagrammatic view showing features embodied in the present invention.

" Fig. Zis a viewsimilarto Fig. 1 showinga difie'rent arrangement of the invention.

Figj 3" is a view sirhilar'to'Figs. hand 2*showing still a further arrangement.

In the operation of high voltage transmission flines'it' isd'esirable to supply currentor potential for'tl'i'e" operation of relays for clearing circuits which are in trouble or become overloaded. Cur- 'rent'for thisp'urp'ose cannot, of course, "be con- Veniently used at line'voltage'and it has been "customary to use'p'otential transformers connected in variousways to step down the voltage, "one method being taconnectthe high voltage side of a potential transformer to each phase of the high voltage line. The low'volta'ge' mndings of the transformers will be connectedin delta;one corner of which is open so"that"an unbalanced voltage'for the differentiphases of thetransmission'line will set up a circulating current in "the delta, this current passing throughsuitable coils in the relay.

In place'of transformers'at high voltage, condensers maybe used with low voltage potential transformers as shown in'Fig. 1 in which the condensers ware shown connectedto the three phases of a high voltage line" through absorbing resistances '11. The current, "after passing through the resistances and condensers, traverses the high potenial windings of transformers 12.

with this arrangement, if the neutralisshifted, due to" a greater electrostatic capacity of some of the conductors to ground, this Will pr'oduce a currentin the transformer secondaries 1-3. This may be oorrectedbvan adjustable load orduty 'place'dfupo'n' the transformers 'as' indicated atjqBO 01" by theuse "of taps 26. Itis'evidentthat the "tap's inay be" placd oirthe' hi'gh Yoltagefvlfihding brine-transformer as at 27. The'corre( :tirig "means may-bearesist'ance, capacity'for reactance as desired; the adjusthienfiheing inade scifthat y the current or voltage under norr'naloperatihg "conditionswill *befi 'e'ducecl to zero or" re a paint sufficiently lowsothatthe "relay"will not cperate until-- an abnormal condition causes an increase incurrentwhich willfopeiate'therelay.

with the 'conden'serso thatunder ther'nost severe disturbances produced by lightning the dronin voltage from conductors to ground'will 'be-flarge- 1y taken'up by the absorbing resistancewithout' "placing a dangerous voltage' upon the" condenser Y5 units. 'Thisfis dire-to the fact thatforai 'giv n voltage" condensers will pass current in proportion tothe frequencyor steepness of wave front. If, therefore; thedisturb'ance si-equi alent to a a very high frequency,- it fisseefl that' this" current b will pass through the condenserwith'out"an"abnormal rise in voltage, and the" current flowing into" the c'oridensnniay" bane-(1e tdproducea very high IR drop in theabsorbin resistance. The 'fiow'of current-tdthe condenser may be very 35 small under normal'operatingconditionssd that the drop in voltage over the'absorb'ing resistance will be" negligible. ,7 V

The transformers" used in series with j'the condensers are frequently provided "with' liiniting iii) gaps 31 as showninj my priorPatent #1,?09i826,

granted April'j 23, 1929. 'Under "an abnormally high voltage surge upon the 'line' the voltage across the transformer primary will" rise until .the limiting gap discharges and relieves the v'olt- '93 age. 'Th drop iri'pbtential is then entirelyac'ross the absorbingresistanoeand' the condenser units. As scones the abmrmai disturbance passes" the current'willbe so limited byth'e condensersat v normal" frequency that the discharge acrossu ie 0 --protectinggap'will clear. The discharges are'of such short duration that in general there is not sufilcient time forthe' operation of I the relays due toan'unbalanced condition from the discharge' of $1.05

thegap. V

One' 'end of'the high potential-winding of each transformer is connected to 'the corresponding ends or the high 'potential 'windings of the other transformersforminga neutral whichis usually n placed in series.

Where a transformer is connected to each phase, considerable care is necessary in order to provide transformers with balanced characteristics as a difference in the magnetizing current or in the ratio will cause a current to flow in the delta winding, even through the low voltage is balanced. With the improved construction shown in Fig. 2, however, it is possible to reduce the number of transformers required to one and since only a single transformer is used, it is not necessary to maintain the same characteristics in a plurality of transformers as in Fig. 1.

In Fig. 2 the low voltage sides of the condensers 10 .are connected to a common point and the primary winding 15 of the transformer is connected to the common point. The high voltage winding of the transformer is protected by a limiting gap 16. .The low voltage winding 17 of the transformer is connected to a relay or other suitable apparatus 19. If desired, the phase angle of the current flowing through the low voltage winding 17 and the relay or other piece of apparatus 19 may be varied by the use of capacity,

reaotance, or resistance as indicated in the drawing. The capacity, reactance or resistance may be placed either in multiple with the load or in series depending upon the characteristics desired.

Where it is not desired to change the phase angle but simply to prevent an abnormally high voltage on the transformer due to open circuit, a resistance may be placed across the winding .17. It is evident that the arrangement of Fig. 2

reduces the transformers required and simplifies the connection to the high voltage line for many installations. 'In' most transmission lines, the

abnormal. voltage between phases is usually limited to very much lower values than the abnormal voltage from the diiferent phases to ground.

During disturbances, 'there is a tendency for all conductors to have at the'same time a higher voltage to ground induced by lightning, although the normal frequency may produce a difference in voltage between the conductors. From this it naturally follows that more insulation is needed between the conductors and ground than between separate conductors making up the different phases of the same system.

In Fig.3 the absorbing resistor units 11 are connected to condensers 20 and 21 which may be The common point 22 is connected to condenser units 23 and 24 which in turn are connected to the primary winding 25 of the transformer. This transformer is protected by a gap 26 and has a low voltage winding 27 which may be used for supplying the desired current or potential for relay operation or other purposes.

The condensers made up of units 23 and 24 may have any suitable relation as compared to the condensers 20' and 21. Where the electrostatic capacity of the condensers 23 and 24 is three times that of the condensers attached to different phases, a uniform rise in voltage on the several phases will produce the same drop in potential on the condensers'above the common point as below the common point. Where the voltage rise is different, the condensers on the ground side of the common point may, however, be of even lower electrostatic capacity, if these condensers will supply the desired current.

This arrangement makes it possible to provide more insulation to ground for a given number of condenser units or a greater range of voltage for a given number of; condenser units between line and ground.

The current or potential supplied by the condenser systems together with their transformers may be used with any suitable relay scheme.

The presentinvention is of especial value when applied to the operation of relays for polyphase transmission lines because by it the voltage made available for relay operation will be propor ,tionalto the drop in voltage of any phase conductor of the system when that phase is grounded.

This is true of the arrangement in which the potential transformers have their high potential windings Y connected and their low potential winding connected in delta, the relay being connected in series with the low potential. winding as shown in Fig. 1. This relation of the voltage in the secondary to the fall in. potential of the grounded phase conductor is true where the potential transformers are connected directly to the conductors of the transmission line in the manner explained even without the interposed-resistance and condensers shown in the drawing; but, where the condensers and resistance are used, the desired result is secured much more economically and with a much greater'degree of reliability than where the transformer windings are connected directly to the transmission'line conductors. It is difficult and expensive toin} sulate a transformer sufiiciently where it is corinected directly to the high potential conductors of modern transmission lines but condensers having high insulating values and consequently good reliability can be produced at comparatively small expense, so that with the arrangement shown in Fig. 1, it is possible to impress a voltage'. on the relay 14, proportional to the drop in voltage on the grounded conductor, at a very considerable reduction in expense and a very considerable gain in reliability over the arrangement in which high potential transformers are connected directly to the transmission'line. v

The. same relation of voltage impressed onfthe relay to the drop in the, potential of the grounded phase conductor is secured in the connection shown in Fig. 2 but with a still further decrease in cost and increase in reliability for thereason that only one transformer is requiredin this case .as compared with three in the connection shown in Fig. 1. h

In Fig. 3, the same ratio of voltagejin the'sec ondary of the transformer to the drop in the conductor is produced but a still greater degree of reliability is secured because of the addition of thecondensers 23 and 24. V y

In the connections shown, it 1 is importantto use condensers of relatively high capacityas comvery satisfactory results. .We' have also found that for satisfactory operation the resistance of the leakage path around the condenser should not be less than approximately forty times the capacity reactance of the condenser for the operating frequency.

The leakage path of a condenser is an uncertain quantity and varies with accumulated surface dirt, weather conditions and other factors. Any unbalance in the leakage paths of the condensers for the different phases in the connections shown will tend to set up a current in the secondary winding of the transformer and this tendency will depend upon the proportion between the conductivity of the leakage paths and the capacity of the condensers. If the connection be used for metering, the error due to leakage will be magnified in direct proportion to the conductivity of the leakage path for a given capacity. It is therefore apparent that the form of condenser used is important and that the conductivity of the leakage path should be kept low for a given capacity. Condensers of very low capacity such as the usual form of bushing insulator are therefore not well suited for this form of connection and it is also important to use condensers, the leakage paths of which are not apt to be materially changed by accumulation of dirt or weather conditions. For this reason, we have found the form of condenser shown in the application mentioned above especially suitable.

We claim:

1. The combination with a polyphase transmission line, of a potential transformer, a plurality of circuits, each of which is connected with one of the conductors of said transmission line, the other end of said circuits being connected together, each of said circuits including condenser in series therewith, a potential transformer having its high potential winding connected with the common point of said circuits, and a condenser interposed in the connection between said high potential winding and said common point.

2. The combination with a polyphase transmission line, of a plurality of circuits, each having one end connected with one phase conductor of said transmission line, said circuits having the other ends thereof joined together, each circuit comprising a resistance and a condenser in series, a potential transformer having one end of the high potential winding thereof grounded and having the other end thereof connected to the joined ends of said circuit, a condenser interposed in series between said high potential winding and the joined ends of said circuits, and a relay connected to the low potential winding of said transformer.

3. The combination with a polyphase transmission line, of a plurality of circuits, each connected to one of the phase conductors of said transmission line, each of said circuits comprising a resistance and a condenser in series, the ends of said circuits opposite said transmission line being joined together, a potential trans- ;former having one end of the high potential winding thereof grounded and having the other end connected through a condenser in series therewith to the joined ends of said circuits, a limiting arcinggap in parallel with said high potential winding, a relay connected with the low potential winding of said transformer, and means for adjusting the phase angle of the current flowing through said secondary winding.

ARTHUR O. AUSTIN. WILLIAM A. HILLEBRAND. 

